Aerts, C. ; Bowman, D. M. ; Símon-Díaz, S. ; Buysschaert, B. ; Johnston, C. ; Moravveji, E. ; Beck, P. G. ; De Cat, P. ; Triana, S. ; Aigrain, S. ; Castro, N. ; Huber, D. ; White, T.

published in Monthly Notices of the Royal Astronomical Society, 476 issue 1, pp. 1234-1241 (2018)

Abstract: We present an 80-d long uninterrupted high-cadence K2 light curve of the B1Iab supergiant ρ Leo (HD 91316), deduced with the method of halo photometry. This light curve reveals a dominant frequency of frot = 0.0373 d−1 and its harmonics. This dominant frequency corresponds with a rotation period of 26.8 d and is subject to amplitude and phase modulation. The K2 photometry additionally reveals multiperiodic low-frequency variability (<1.5 d−1) and is in full agreement with low-cadence high-resolution spectroscopy assembled during 1800 d. The spectroscopy reveals rotational modulation by a dynamic aspherical wind with an amplitude of about 20 km s−1 in the H α line, as well as photospheric velocity variations of a few km s−1 at frequencies in the range 0.2–0.6 d−1 in the Si iii 4567 Å line. Given the large macroturbulence needed to explain the spectral line broadening of the star, we interpret the detected photospheric velocity as due to travelling superinertial low-degree large-scale gravity waves with dominant tangential amplitudes and discuss why ρ Leo is an excellent target to study how the observed photospheric variability propagates into the wind.

Keyword(s): asteroseismology ; techniques: photometric ; techniques: spectroscopic ; stars: massive ; stars: oscillations ; stars: rotation
DOI: 10.1093/mnras/sty308
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